After analyzing word lists covering nearly two-thirds of the world’s languages, researchers found that unrelated languages very often use or avoid the same sound for specific referents.

“For instance, words for tongue tend to have l or u, ‘round’ often appears with r, and ‘small’ with i,” study authors write in Proceedings of the National Academy of Sciences. “These striking similarities call for a reexamination of the fundamental assumption of the arbitrariness of the sign.”

Researchers note that, prior to the study, it was widely assumed that one of the core properties of spoken language is the arbitrary relation between sound and meaning.

“Some exceptions in the form of nonarbitrary associations have been documented in linguistics, cognitive science, and anthropology, but these studies only involved small subsets of the 6,000+ languages spoken in the world today,” the study continued.

Dr. Lynne Cahill, a lecturer in English and linguistics at the University of Sussex in England, told The Telegraph it’s possible that some words were similar across languages because they’re the first noises children make. It’s still too early to positively identify a universal root for other words, she said.

“You could argue that the words chosen here are very old and therefore most likely to have a common ancestor language in the past, from which they all derived,” Cahill said. “I think this is an interesting study which has looked at so many different languages but I don’t think it quite justifies their claim that it debunks the idea that language is arbitrary and I think they looked at too few words to make any firm conclusions.”